Posterior stability in fixed-bearing versus mobile-bearing total knee replacement: a radiological comparison of two implants.

INTRODUCTION: Posterior tibial translation in total knee replacement (TKR) could be one major factor for PE wear, delamination and loosening of the tibial component due to increased shear forces and component-to-bone interface stress. The aim of this study was to assess the posterior stability of two different designs of posterior cruciate ligament (PCL) substituting TKR. METHOD: In this non-randomised consecutive study 43 patients underwent TKR for primary osteoarthritis. Twenty-six patients in group FB received a deep-dished fixed-bearing Duracon TKR (Howmedica, Rutherford, NJ, USA) and 17 patients in group MB a deep-dished rotating mobile-bearing Duracon TKR. In both groups the PCL was resected. All patients had pre- and postoperative kneeling stress radiographs and were clinically evaluated with the Knee Society Score. Posterior tibial translation was measured by tracing a line along the posterior tibial cortex in relationship to the posterior edge of Blumensaat's line. RESULTS: The average follow-up was 13 months for group FB and 11 months for group MB. Both groups demonstrated a statistical significant increase of the mean posterior tibial translation on kneeling stress X-ray of 4.1 mm (group FB) (P < 0.001) and of 6.6 mm (group MB) (P < 0.001) compared to pre-operative. Group MB showed a significant higher posterior draw (P < 0.008). Clinical assessment using the Knee Society Score showed comparable short-term results. CONCLUSION: The deep-dished fixed-bearing TKR as well as the deep-dished rotating mobile-bearing TKR demonstrated significant posterior tibial translation on kneeling stress X-ray. It remains to be determined what amount of joint play is optimal for clinical function and to minimise shear forces and PE wear. Moreover the amount of posterior tibial translation was significantly higher with the mobile-bearing insert, which could be directly related to the asymmetric rotational mobility of the tibial insert. A long-term follow-up is necessary to investigate whether our findings correlate with the survival-rate of these specific implants.

Assessment of posterior stability in total knee replacement by stress radiographs: prospective comparison of two different types of mobile bearing implants.

The aim of this study was to assess the posterior stability of two different designs of total knee replacement (TKR) with deep-dished mobile bearing (MB) implants using stress X-rays. In a prospective non-randomized consecutive study, 34 patients with primary osteoarthritis of the knee underwent TKR. In group A (17 knees), they received a MB insert with a Duracon prosthesis and in group B (18 knees), a Genesis prosthesis. In all cases the posterior cruciate ligament (PCL) was resected. All patients had pre- and post-operative kneeling X-rays and were clinically evaluated with the Knee Society Score. Measurements on the radiographs were taken by tracing a line along the posterior cortex of the tibia and then measuring the perpendicular distance to a point marked at the posterior corner of Blumensaat's line. The average follow up was 10.7 months for group A and 5.4 months for group B. No statistical difference could be found in terms of clinical results and pre- and post-operative kneeling X-rays between the two groups. In each group, all knees demonstrated a significant posterior tibial translation postoperatively compare to their pre-operative status (p<0.0001). There are advantages in resecting the PCL in TKR: mobile flexion gap, correction of fixed deformity, more flexibility to adjust the joint line. The use of a deep dished polyethylene (PE) insert provides stability and use of MB insert reduces PE wear whilst retaining congruity. Two designs of deep-dished MB inserts showed significant posterior tibial translation on stress X-rays. It remains to be determined what amount of laxity is optimal for clinical function and polyethylene longevity.

Transchondral drilling for osteochondritis dissecans of the medial condyle of the knee.

Osteochondritis dissecans is a rare condition which occurs most frequently in the medial condyle of the knee. Its prognosis remains controversial. We report our experience with transchondral drilling (TCD) for osteochondritis dissecans. The rationale for this low-morbidity procedure is to enhance the healing potential of a lesion which failed to heal after conservative treatment. This multicenter retrospective study examined 24 patients (25 medial condyles), including cases both before (juvenile osteochondritis dissecans, JOCD; n=17) and after closure of the physis (adult osteochondritis dissecans, AOCD; n=8). All patients initially underwent a prolonged conservative treatment. The mean duration of symptoms prior to surgery was 22 months in JOCD and 55 months in AOCD patients. TCD was proposed in cases of intact or almost intact articular cartilage and was initially conducted under arthrotomy and later by arthroscopy. Mean follow-up time was 11.8 years in JOCD and 6 years in AOCD, and evaluation was based on clinical examination and radiography. Excellent clinical results were only observed in the JOCD group (12/17). In the AOCD group 4 patients had a good result and the other 4 a poor result. Radiological findings matched with clinical results. Except for age, factors of poor prognosis were: fissure of the articular cartilage and anterior extension of the lesion. We do not recommend TCD for AOCD. In JOCD, failure after 12 months of conservative treatment should indicate TCD in the cases where the cartilage remains continuous. At this stage there is no indication for more aggressive procedures.

Long-term disability assessment after surgical treatment of low grade spondylolisthesis.

The aim of this study was to determine whether assessment of back surgery with disability scores is relevant. We also attempted to answer the question of whether this evaluation should be conducted by a surgeon or a medical doctor. This retrospective study analyzes the long-term outcome (average follow-up 7 years, range: 3-12) of 40 patients (mean age: 46.2 years) treated by posterior surgical decompression, posterolateral arthrodesis, with or without instrumentation, for symptomatic low-grade spondylolisthesis. All patients were interviewed postoperatively and examined the same day by an orthopedic surgeon, who was not involved in the patients' treatment, as well as by a medical doctor rehabilitation specialist. Impairment was assessed by a standardized clinical examination and by visual analog scales (VAS) of pain. Disability was assessed using two scales: the Quebec disability scale and the Beaujon scale. Anxiety and depression were assessed with a validated specific questionnaire (HAD). Patient's perceived handicap was assessed on a 100-mm VAS. Our results show that the scores of the two disability scales were highly correlated with the patient's overall satisfaction ( r = 0.73 and 0.77 for the Quebec scale and the Beaujon scale, respectively). The intraclass correlation coefficient showed very good or excellent correlation between the data collected by the surgeon and the rehabilitation specialist, ranging from 0.8 to 0.97. This finding clearly demonstrates that interview by a surgeon who is not involved in the patient's treatment does not influence the patient's assessment in terms of impairment, disability, or handicap. Moreover, our results suggest that disability scales are the most relevant outcome measures in the assessment of spine surgery.

Coral grafting supplemented with bone marrow.

Limited success in regenerating large bone defects has been achieved by bridging them with osteoconductive materials. These substitutes lack the osteogenic and osteoinductive properties of bone autograft. A direct approach would be to stimulate osteogenesis in these biomaterials by the addition of fresh bone-marrow cells (BMC). We therefore created osteoperiosteal gaps 2 cm wide in the ulna of adult rabbits and either bridged them with coral alone (CC), coral supplemented with BMC, or left them empty. Coral was chosen as a scaffold because of its good biocompatibility and resorbability. In osteoperiosteal gaps bridged with coral only, the coral was invaded chiefly by fibrous tissue. It was insufficient to produce union after two months. In defects filled with coral and BMC an increase in osteogenesis was observed and the bone surface area was significantly higher compared with defects filled with coral alone. Bony union occurred in six out of six defects filled with coral and BMC after two months. An increase in the resorption of coral was also observed, suggesting that resorbing cells or their progenitors were present in bone marrow and survived the grafting procedure. Our findings have shown that supplementation of coral with BMC increased both the resorption of material and osteogenesis in defects of a clinical significance.

The medial and inferior calcaneal nerves: an anatomic study.

The existence of chronic heel pain induced by the compression of nerves prompted us to conduct an anatomic study of the innervation of the heel. Fifteen cadaver feet were dissected to investigate the origin, course and branches of the medial calcaneal nerve (MCN) and the inferior calcaneal nerve (ICN). Despite a variable origin (tibial n. (TN) or lateral plantar n. (LPN)), the medial calcaneal nerve branches which lay superficial to the abductor hallucis muscle (AH) were quite constant. The medial calcaneal nerve gave branches to the abductor hallucis muscle and innervated the posterior part of the medial face of the heel. It terminated in the superficial heel pad at the inferior part of the heel. In our study, the inferior calcaneal nerve always originated from the lateral plantar nerve. Its relationship to the deep fascia of the abductor hallucis muscle and anterior tubercle of calcaneus may explain the entrapment syndrome of the inferior calcaneal nerve.