Effect of external extra-articular ligament plasty on the results of anterior cruciate ligament reconstruction with patellar tendon, a 4 years follow-up

PURPOSE OF THE STUDY: The purpose of this study was to compare the functional results obtained when an external extra-articular plasty was added to an anterior cruciate ligament (ACL) reconstruction using an autologous bone tendon-bone patellar tendon graft. MATERIAL AND METHODS: The authors analyzed two consecutive series of 60 and 50 patients operated by the same surgeon for a chronic rupture of the anterior cruciate ligament, one by reconstruction of the cruciate ligament with a free graft of the patellar tendon supplemented by an external extra-articular plasty made with a quadriceps tendon graft and the second with an isolated free patellar tendon graft. Anterior laxity was measured before and after surgery, by dynamic X-rays and by the Medmetric KT-1000 arthrometer. Functional results were evaluated four years after operation, with the French A.R.P.E.GE score based on sport activity level and intensity. RESULTS: Anterior laxity was not different before operation in both groups and there was no difference between males and females. Medmetric KT-1000 arthrometer showed the same negative differential laxity immediately after surgery in both groups and the same evolution during the first 4 years, without any significant difference on laxity on the middle aspect of the knee. Radiological results were different. After a 4 years follow-up, anterior laxity did not show significant difference on the medial compartment of the knee (5.3 +/- 2.3 mm and 5.5 +/- 1.7 mm), but there was a significant minor laxity in the lateral compartment for the lateral extra-articular plasty group (11.0 +/- 2.3 mm against 14.8 +/- 3.8 mm)(p = 0.002). Functional results and sport activity were similar in both groups. Examination showed 4 positive pivot shift tests (2 "sliding" and 2 positive) in the group with extra-articular plasty, even though 8 positive pivot shift tests in the isolated ACL group (5 "sliding" and 3 positive) were found. DISCUSSION: This study, as well as five others studies found in literature, was not randomized. In all these series, the surgical techniques, the rehabilitation programs and the functional score evaluation were too different to allow any pertinent comparison. Extra-articular plasty helps to control the laxity of the lateral compartment of the knee which is incompletely controlled by ACL reconstruction, particularly in chronic cases. This is proved by radiological measurements and pivot shift tests. Jensen in 1983, about 205 patients with a 4 year follow-up and Noyes, which used an allograft patellar tendon, found an advantage to do extra-articular plasty. But Strum (in 1989), as O'Brien (in 1991) and Roth (in 1987), did not found any advantage with extra-articular plasty. CONCLUSION: It is therefore obvious, after a four-year follow-up, that extra-articular supplementation presents an advantage for reconstruction of the ACL. by a free graft of the patellar tendon in chronic cases. Further randomized study will confirm that isolated ACL reconstruction is possible in some well defined categories of anterior laxity.     

Outcome and clinical signs of arthroscopically graded patellar chondromalacia with or without lateral release

In a follow-up study of 67 patients with an arthroscopically diagnosed patellar chondromalacia, we compared the results of plain conservative treatment with those after an open lateral retinacular release. The mean follow-up was 35 months. In Grade I chondromalacia the lateral release did not affect the result, which was in all cases good or excellent. In Grade II to IV chondromalacia the lateral release appeared beneficial, although the difference did not reach statistical significance. We also examined the validity of three clinical signs in arthroscopically verified patellar chondromalacia. Patellar inhibition and tracking tests were clearly more sensitive than the lateral apprehension test, which often gave a false negative result. If the patellar inhibition test is positive and a Grade II to IV chondromalacia of the patella is found at arthroscopy, lateral release should be considered among other procedures, like patellar shaving or patellar resurfacing.     

A morphometric study of the femoro-patellar joint from lateral x-ray view

PURPOSE OF THE STUDY: The goal of this study was to specify criteria of femoro-patellar joint normality on lateral view. MATERIAL: This study was based on radiological examination of 102 knees in 51 adults (average age 26.1 years). It concerned 29 women and 22 men that had never suffered from their knee and were supposed healthy. METHODS: The radiological protocol was the following: a lateral view at 45 degrees of flexion, two lateral views in extension, with and without quadriceps contraction. The analysis was focused on patellar surface aspect, its height, its depth and covering measurement. RESULTS: We found 83.7 per cent of so-called "normal" patellar surface, and 12.7 per cent of "abnormal" patellar surface (dysplasia) in the absence of pain. DISCUSSION: We have confirmed figures advanced in others series of the literature concerning patellar height and patellar surface, as well as patellar surface depth and covering. We have underlined the interest of lateral views; in extension with quadriceps contracted and relaxed. Finally, we have defined a trochleo-patellar sign that allows to correlate patellar height to patellar surface height (ITP = 0.35 to 0.84). CONCLUSION: This study insists on the interest of radiological lateral views of the knee and determine criteria for normalities.     

Bone tunnel enlargement after anterior cruciate ligament reconstruction with semitendinosus tendon using Endobutton fixation on the femoral side

We evaluated 29 knees with a minimum follow-up of 2 years after anterior cruciate ligament (ACL) reconstruction using doubled autogenous semitendinosus tendons. On the femoral side, a 5-mm Mersilene tape (Ethicon, Norderstedt, Germany) with an Endobutton (Acufex Microsurgical, Mansfield, MA) was used. The tendon was fixed on the tibial side with two staples. Regarding the IKDC score, 66% of the patients were graded as normal or nearly normal. The anterior laxity side-to-side difference (KT 1000, man-max-drawer) was under 3 mm in 55% and under 5 mm in 90%. Radiographs taken in the lateral and anteroposterior projections of the knee showed sclerotic bone tunnel margins. The diameter of the bone tunnels were measured, corrected for magnification, then compared with the original reamed diameter to determine any change in size. Enlargement of at least 2 mm was identified in 72% of the femoral tunnels and 38% of the tibial tunnels. No correlation was found concerning the enlargement of the tunnel and the IKDC score or the residual joint laxity. We conclude that using an Endobutton-Mersilene construct in ACL reconstruction leads to femoral and tibial bone tunnel enlargement at follow-up of 2 years.     

Placental restriction alters adrenal medullary development in the midgestation sheep fetus

This is a retrospective study of 10 patients with combined cruciate ligament and posterolateral instability who underwent surgical reconstruction between 1991 and 1994. All knees had at least 20 degrees increased external rotation at 30 degrees of knee flexion and from 1+ to 3+ varus instability. Five knees with posterior cruciate ligament ruptures had at least a 2+ Lachman test result. (One knee had both anterior and posterior cruciate ligament injuries). In all cases the lateral collateral ligament was reconstructed with a bone-patellar tendon-bone allograft secured with interference screws. Fixation tunnels were placed in the fibular head and at the isometric point on the femur. The cruciate ligaments were reconstructed with autograft or allograft material. The average follow-up was 28 months. Excessive external rotation at 30 degrees of flexion was corrected in all but one knee. Six patients had no varus laxity, and four patients had 1+ varus laxity at 30 degrees of flexion. The posterior drawer test result decreased, on average, to 1+, and the Lachman test result decreased to between 0 and 1+. The average Tegner score was 4.6, with five patients returning to their preinjury level of activity and four returning to one level lower. These results indicate that this is a promising new procedure for patients with instability resulting from lateral ligament injuries of the knee.     

Comparison of arthroscopic and open reconstruction of the anterior cruciate ligament. Early results

The purpose of this study was to determine in a prospective, randomized, blinded design whether arthroscopically assisted anterior cruciate ligament reconstruction offered any significant immediate or short-term advantages over traditional open reconstruction through a limited arthrotomy. Patients with a diagnosis of deficiency of the anterior cruciate ligament were randomly assigned to one of two treatment groups: the open group (limited open reconstruction) or the arthroscopic group (fully arthroscopic reconstruction). Postoperatively, both groups were treated identically. Intra- and postoperative observations included length of surgery, duration of hospitalization, and amount of pain medication. Follow-up evaluations were performed at 1, 6, 12, 16, 20, and 24 weeks to record crepitus, swelling, range of motion, ligament laxity, and thigh atrophy. Lysholm scores were obtained at the 16 and 24 week follow-ups. At 24 weeks, 86% of the open group and 89% of the arthroscopic group had good-to-excellent results. Intraoperative, postoperative, and follow-up findings indicated no statistically significant differences or relationships between the two groups in any of the variables measured, except that operative time was 13 minutes longer in the arthroscopic group (P < 0.001). The results do not substantiate a clinical advantage for either technique.     

Anterior cruciate ligament reconstruction with autogenous patellar tendon graft in patients with articular cartilage damage

To test if anterior cruciate ligament reconstruction with autogenous patellar tendon can alleviate symptoms and functional limitations and increase activity levels in patients with advanced articular cartilage damage, we looked at 53 patients with arthroscopically documented cartilage damage. In this group, a mean of 7.5 years had elapsed between the original injury and the reconstruction, and 90 prior operative procedures had been done. Postoperatively, all patients had immediate motion and early functional rehabilitation. The results were assessed with the Cincinnati Knee Rating System. At followup (mean, 27 months), significant improvements were found for pain, swelling, giving way, functional limitations with daily and sports activities, and the overall rating score. Forty-two patients (79%) had returned to some type of athletic activity. Only three patients (6%) had failed results. In the patients' own ratings of the overall knee condition, 8 of 51 (16%) rated their knees as normal, 28 (55%) as very good, 7 (14%) as good, 5 (10%) as fair, and 3 (6%) as poor. We concluded that the majority of patients benefited from the arthroscopically assisted anterior cruciate ligament reconstruction because it decreased episodes of giving way with daily activities and increased activity without aggravating the preexisting arthrosis.     

Mid-term outcome after surgically managed re-rupture of the anterior cruciate ligament

This retrospective study shows the results in 30 patients of revision surgery on their reruptured ACL. The follow-up time was 30 months on average (range 10-54 months). The follow-up examination included subjective (Lysholm score, Tegner activity level rating score), clinical and radiological criteria and also instrumental laxity testing with the KT-1000 arthrometer. The overall evaluation was done according to the IKDC score. The follow up showed subjective and objective results almost equal to those after primary surgery on ACL. The IKDC score revealed certain abnormal and highly abnormal results, which demonstrated that revision ACL surgery gives poorer results than primary surgery. Nevertheless, we recommend reconstruction of a torn ACL even in a revision case to restore the knee function and prevent further menisceal and chondral damage and degeneration.     

The effects of knee reconstruction on combined anterior cruciate ligament and anterolateral capsular deficiencies

We tested the effect of intraarticular reconstructions of the anterior cruciate ligament alone and in combination with extraarticular reconstructions in 10 cadaveric knees. These knees had anterior cruciate ligament deficiency alone or in combination with anterolateral capsuloligamentous deficiencies. In the knees with combined injury, intraarticular reconstruction returned anterior stability to levels not significantly different from levels found for the knees deficient in the anterior cruciate ligament alone and treated with this procedure. After intraarticular reconstruction, rotational stability of the knee with combined injuries failed to return to the levels seen in the knee with isolated anterior cruciate ligament deficiencies that underwent the same treatment. When a tenodesis with either 0 N or 22 N of tension was added to the intraarticular reconstruction in the knee with combined injuries, we found that excessive internal rotation significantly decreased at all angles of flexion, except at full extension with 0 N of tension. In addition, the extraarticular reconstruction with 22 N of tension in the tenodesis overconstrained the knee in internal rotation between 30 degrees and 90 degrees of knee flexion. The tenodesis with 0 N of tension overconstrained the knee at only 60 degrees and 90 degrees of flexion. These results suggest extraarticular reconstruction as an adjunct to the intraarticular operation for the knee with anterior cruciate ligament and anterolateral structural injuries. The results also suggest that the surgeon can affect anterior and rotational laxity by adjusting the tension in the tenodesis.     

The outcome of operatively treated anterior cruciate ligament disruptions in the skeletally immature child

The purpose of this study was to evaluate the outcome of transphyseal ligament reconstruction in skeletally immature children with midsubstance anterior cruciate ligament (ACL) disruption. Five consecutive patients (mean age, 12.9 years; range, 8 to 14 years) with radiographically documented "wide" open growth plates and a minimum of 5 cm of expected remaining growth, underwent intra-articular reconstruction of the ACL. Operative treatment included three ACL reconstructions using hamstring tendons and two with quadriceps patellar tendon. All involved a centrally placed 6-mm or smaller tibial drill hole through an open physis and graft placement in an over-the-top position on the femur. At an average follow-up of 7.4 years (range, 4.5 to 9.9 years), no patient had a positive anterior drawer, Lachman, or pivot shift test. On KT-1000 arthrometer testing, all patients had 3 mm or less of increased anterior-posterior displacement (mean +/- SD = 1.0 +/- 1.6 mm). Magnetic resonance imaging showed that four tibial physes had fused in a symmetric fashion and one was still open. Orthoroentgenograms showed that no patient had a significant leg length discrepancy (-0.8 mm +/- 3.4 mm). The mean increase in height postoperatively was 17.7 cm (range, 7.6 to 31.0 cm). Overall, using the International Knee Documentation Committee (IKDC) evaluation form, there were four patients with grade A and one with grade C. The one patient with a poor IKDC grade had sustained a subsequent patellar dislocation with osteochondral fracture. In conclusion, ACL reconstruction using small drill holes placed through open tibial physes does not seem to adversely affect outcome or future growth.     

Principles and value of isokinetic evaluation in ruptures of the anterior cruciate ligament

Isokinetic muscular evaluation allows to appreciate the knee joint functional patterns in conditions close to sports activities. Analyzing bilateral symmetry and agonist/antagonist ratios of the lower extremity, this method is a useful index for the objective evaluation of ligament-deficient knees. 106 patients with a chronic ACL deficient knee sustained a presurgery isokinetic evaluation. 94 patients had a post-operative evaluation and 13 a pre and post-surgery evaluation. All patients were simultaneously evaluated by clinical examination and measures of instrumental knee laxity (KT 1000). Results showed that isokinetic performance was not correlated to the objective laxity as measured with the KT 1000 but was correlated to 1) the type of laxity (i.e. associated postero-lateral laxity), 2) the functional level of activity, and 3) the time of disability. Best functional results were obtained in patients whose injured knee hamstring/quadriceps (H/Q) ratio was close to the uninjured knee H/Q ratio. The mean quadriceps deficit was over 15 per cent for 75 per cent of the patients one year after surgery, and for 50 per cent of the patients after two years. The quadriceps deficit was not parallel to the length of the autograft taken from the extensor mechanism. Isokinetic evaluation is a guideline for rehabilitation allowing specific strengthening of the weaker muscular groups.     

Complications from the hinged GUEPAR prosthesis after resection of knee tumor. 102 cases

PURPOSE: The purpose of this study was to present the complications which occurred in knee replacement with the GUEPAR prosthesis, after bone tumor resection. We tried to point out complications in relation to prosthetic design and surgical technique. MATERIAL AND METHOD: Between 1972 and 1993, 90 patients had a knee resection, for 80 malignant and 10 benign tumors. There were 51 males and 49 females, aged 12 to 75 years (mean age 35). Fifty-six distal femur resections and 34 proximal tibial resections were performed. Length of resection averaged 16 cm (9 to 30). The reconstruction was always achieved with a cemented, custom-made GUEPAR prosthesis. Including revisions, there was a total of 102 prostheses in 90 patients. A patellar resurfacing was performed in 64 cases. An allograft reconstruction was associated in 39 knees. In all tibial resections and in two extra-articular femoral resections, the extensor mechanism had to be reconstructed. Several reconstruction techniques were associated, in which 19 medial gastrocnemius transfers. The prosthesis design was slightly modified with time. Ten patients received radiotherapy, and 55 had chemotherapy. RESULTS: Results and complications were retrospectively assessed, with an average follow-up of 4.3 years (1 to 22). Six patients were lost for follow-up, 62 patients were alive, with no evolutive disease, 13 had an evolutive disease and 10 were deceased from disease. Nineteen patients had distant metastasis and 17 had local recurrences. Apart from intraoperative complications, late mechanical complications included: 13 aseptic loosening, 2 femoral shaft fractures, 18 knee contractures, 5 femoral stem fractures and, 18 intra-articular instabilities related to wear of the hinge-axis. In the 39 allograft-composite prostheses, only 15 had a favorable evolution. There were 15 extensor mechanism failures and 13 knees had persistent infection. There was a total of 94 reoperations in the 90 patients. In 28 cases, the initially implanted prosthesis was removed. There were also 18 revisions, 7 amputations and 3 arthrodeses. Survivorship analysis showed a 60 per cent probability for the initial prosthesis not to be revised at 10 year-follow-up, apart from oncologic complications. DISCUSSION: Results with allograft-composite reconstruction were not better than with massive prosthesis. When needed, soft tissue coverage and patellar tendon augmentation would better be performed with gastrocnemius plasty. Polyethylene and steel bushes were not solution for hinge axis wear.     

Functional disorders of the foot after tenodeses: is the method still currently acceptable?

On the basis of biomechanical and clinical studies, this article discusses the relevance of tenodesis in the operative treatment of chronic lateral ankle instability. Considering the experimental results, it is evident that any tenodesis leads to restriction of inversion according to the course and the tightness of the graft. It has been shown that the lateral peroneal reconstruction has a negative influence on the kinematic coupling of the ankle joint complex. The data of the clinical studies reflect the biomechanical results. Despite a high rate of satisfaction, up to 50% of the patients reveal a restriction of inversion. Some authors, particularly those who report on a 10-year follow-up, showed that the degree of arthrosis increased and that deterioration of the clinical result occurred over the time. The measurement of plantar pressure distribution during gait proved the alteration of foot biomechanics. The biomechanical and clinical data available on tenodesis and the good results of the anatomical repair suggest that tenodesis is presently only the method of last choice.     

Mortality following elective infrarenal aortic reconstruction: a Joint Vascular Research Group study

BACKGROUND: This study aimed to define the cause of death in patients undergoing elective infrarenal aortic reconstruction. METHODS: Members of the Joint Vascular Research Group who had collected details prospectively of patients undergoing elective aortic reconstruction provided information on those who died. RESULTS: Details of 3786 patients were obtained. Some 171 patients died (133 following abdominal aortic aneurysm (AAA) and 38 after aortofemoral bifurcation graft (AFBG) for occlusive disease). The mortality rate following AAA repair was 4.8 per cent, rising to 16 per cent if repair was combined with either renal or distal reconstruction (P < 0.001). Similar results were obtained with AFBG (3.4 and 11 per cent respectively, P < 0.001). The first major complication encountered was cardiac (39.8 per cent), followed by bleeding (20.5 per cent), respiratory (13.5), and gut (5.3 per cent), or limb ischaemia (6.4 per cent). Bleeding was commoner following reconstruction for aneurysm compared with that for occlusive disease (P < 0.05). Eighty-six patients (50.3 per cent) died from the first major complication. Of the remainder, 45 (53 per cent) developed multisystem organ failure (MSOF). The most commonly involved systems were cardiac, respiratory and renal. CONCLUSION: Cardiac problems were the major cause of death following infrarenal aortic reconstruction. MSOF is the 'final common pathway' in about half of the patients who survive the initial complication.     

Evaluation of the medial soft-tissue restraints of the extensor mechanism of the knee

We performed an anatomical dissection of the medial soft-tissue retinacular fibers that restrain lateral patellar displacement and found that the medial patellofemoral ligament inserts not only on the patella but also on the undersurface of the distal aspect of the quadriceps mechanism. The deep capsular layer contained substantial retinacular fibers that were associated with the medial patellomeniscal ligament. Functional studies of the relative contributions of the medial soft-tissue restraints in the prevention of lateral patellar displacement were also performed. Twenty-five fresh-frozen specimens of the knee, obtained after amputations (nineteen specimens) or from cadavera (six specimens) were tested biomechanically on a universal testing instrument. We ranked the soft-tissue restraints, in order of their relative contributions to the restraining force, on the basis of the percentage of force provided by the retinacular and ligamentous tissue that resisted the lateral displacement of the patella. The medial patellofemoral ligament, although varying in size and importance, was found to be the major medial soft-tissue restraint that prevented lateral displacement of the distal knee-extensor mechanism, contributing an average of 53 per cent of the total force. The patellomeniscal ligament and associated retinacular fibers in the deep capsular layer of the knee, which were previously thought to be functionally unimportant in the stabilization of the patella, contributed an average of 22 per cent of the total force. The previously described retinacular fibers (the patellotibial band) were functionally unimportant in the prevention of lateral displacement.     

Prosthetic knee replacement after resection of a malignant tumor of the distal part of the femur. Medium to long-term results

We evaluated the medium to long-term results of treatment with a custom prosthetic knee replacement after wide resection of a primary malignant tumor of the distal part of the femur in forty consecutive patients. The duration of follow-up ranged from five to seventeen years (median, eight years). At the time of the latest follow-up, thirty-five (88 per cent) of the forty patients were free of disease and five (13 per cent) were alive with metastatic disease. No local recurrence was observed. Twenty early complications occurred in eighteen patients (45 per cent). Aseptic loosening of the femoral component, which necessitated a revision in eleven patients at an average of fifty-one months, was the most frequent mode of failure. The rate of prosthetic survival, as estimated with use of the Kaplan-Meier method, was 85, 67, and 48 per cent at three, five, and ten years. Univariate analysis demonstrated that the rate of prosthetic survival was significantly worse for male patients, for those in whom at least 40 per cent of the femur had been resected, for those who had had total resection of the quadriceps muscles or subtotal resection (preservation of only the rectus femoris muscle), and for those in whom a straight femoral stem had been used (p < 0.05 for all comparisons). Multivariate analysis showed that the independent adverse prognostic factors for prosthetic survival were male gender, resection of at least 40 per cent of the femur, and fixation of the femoral stem with cement. The rate of limb salvage was calculated, with use of the Kaplan-Meier method, to be 93 per cent at three years and 90 per cent at five and ten years. At the latest follow-up examination, the functional scores according to the classification system of the Musculoskeletal Tumor Society ranged from 14 to 29 points; the mean was 24 points, which represents function that is 80 per cent that of normal. The mean scores in the categories of walking supports and gait were better for the patients in whom the quadriceps muscles had been preserved than for those who had had total or subtotal resection of those muscles. Although advances in imaging and local therapy narrow the indications for an extra-articular resection of a tumor, the implant that was used in the present study continues to be used in approximately 15 per cent of patients who have a fracture or an intra-articular extension of the tumor that necessitates extensive extra-articular resection.     

Instrumented measurement of patellar mobility

To provide an objective analysis of medial and lateral patellofemoral laxity, we examined 94 uninjured athletic subjects and 22 patients with unilateral lateral patellar dislocation. We developed an instrument to measure the compliance of the medial and lateral patellar restraints. The instrument recorded the force-displacement relationship as the patella was pushed medially and laterally. Subtracting the medial displacement from the lateral displacement at a given force level allowed the tester to assess the peripatellar soft tissue "balance." The results for both the 2.5- and the 5-pound tests were significant. Paired comparisons differentiated the three groups, with significant differences between control and affected (P = 0.0001), control and contralateral (P = 0.0036), and affected and contralateral (P = 0.0157) knees. The mean result of the lateral minus medial displacement test for our sample population of control subjects was -2.1 mm for the 5-pound test. A negative value in this test indicates that medial displacement exceeds lateral displacement. This finding was present in 81% of control subjects. In contrast, the mean result for the patients' affected knees was +3.2 mm for the 5-pound test. Using the value of 0.0 mm as the diagnostic determinant for peripatellar imbalance, we found a test sensitivity of 91% and a specificity of 81%.     

Quadriceps atrophy after partial resection of the patellar tendon: an experimental study in a rat model

Quadriceps muscle atrophy of rats was examined after resection of the central third (group 1) or the lateral two thirds (group 2) of the patellar tendon, the tensor fascia lata (group 3), or the medial hamstring (group 4). The quadriceps atrophied in groups 1 and 2, and more so in group 2, but there was no atrophy in groups 3 or 4. Thus, after an anterior cruciate ligament reconstruction procedure using the patellar tendon, resection of the patellar tendon itself leads to quadriceps atrophy and the extent of atrophy is related to the resected width.     

Patterns of meniscal tears associated with anterior cruciate ligament lesions in athletes

In this study, 400 clinically anterior cruciate ligament (ACL) deficient knees were arthroscoped and studied prospectively in the period January 1986 to April 1992. An ACL tear was always confirmed, and 41 per cent of these patients did not have an associated meniscal tear. In 30.25 per cent the lateral meniscus was torn; in 21.25 per cent the ACL tear was associated with a medial meniscus tear, and in the remaining 7 per cent both menisci were torn. The most frequently associated meniscal injury was the bucket handle tear of the medial meniscus (9 per cent), followed by the posterior horn tear of the lateral meniscus, which showed the same frequency as the ragged (or degenerated) tear of the lateral meniscus (6 per cent). The horizontal tear of the posterior part of the lateral meniscus showed a prevalence of 4.3 per cent. This picture is probably dependent on a secondary referral nature of the centre surveyed, in which the average time between injury and arthroscopy was 23.3 months.     

Porous-coated metal-backed patellar components in total knee replacement. A postmortem retrieval analysis

The use of porous-coated metal-backed patellar components to achieve consistent fixation by bone ingrowth and to provide relief of pain warrants serious scrutiny. We conducted a quantitative postmortem investigation of eleven consecutively retrieved components with use of high-resolution contact radiographs, electron microscopy, and histological analysis. The implants had been in situ for a mean (and standard deviation) of 45+/-36 months (range, one to eighty-four months). Analysis of the high-resolution contact radiographs revealed that a mean of 86+/-12 per cent (range, 61 to 100 per cent) of the porous coating was in contact with the host bone. Backscattered electron imaging showed that the mean volume fraction of bone ingrowth was 13+/-9 per cent (range, 0 to 30 per cent). No significant difference was detected, with the numbers available, between the volume fraction of the bone ingrowth measured in the porous coating and that of the host cancellous bone in the patellae.