Severe Heterotopic Ossification following Total Knee Replacement.

Although the incidence of minor heterotopic ossification is probably higher than what is usually expected, severe heterotopic ossification (HO) is an extremely rare event following total knee replacement surgery. We present the case of a 66-year-old woman who initially had achieved an excellent range of motion following bilateral uncemented rotating platform total knee replacement, before presenting with pain and loss of range of motion at 2 months after surgery. Severe HO was diagnosed on X-rays. Treatment consisted of nonoperative measures only, including physiotherapy with hydrotherapy and anti-inflammatories. She eventually regained her range of motion when seen at 8 months after operation. This case illustrates that nonoperative treatment without the use of radiotherapy or surgery can be used to safely resolve stiffness caused by HO after total knee replacement.

Biomechanical testing of implant free wedge shaped bone block fixation for bone patellar tendon bone anterior cruciate ligament reconstruction in a bovine model.

BACKGROUND: The use of an interference fit wedged bone plug to provide fixation in the tibial tunnel when using bone-patellar tendon-bone autograft for anterior cruciate ligament reconstruction offers many theoretic advantages including the potential to offer a more economical and biological alternative to screw fixation. This technique has not been subjected to biomechanical testing. We hypothesised that a wedged bone plug fixation technique provides equivalent tensile load to failure as titanium interference screw fixation. METHODS: In a controlled laboratory setting, anterior cruciate ligament reconstruction was performed in 36 bovine knees using bone-patella-bone autograft. In 20 knees tibial fixation relied upon a standard cuboid bone block and interference screw. In eight knees a wedge shaped bone block with an 11 mm by 10 mm base without a screw was used. In a further eight knees a similar wedge with a 13 mm by 10 mm base was used. Each specimen used a standard 10 mm tibial tunnel. The reconstructions were tested biomechanically in a physiological environment using an Instron machine to compare ultimate failure loads and modes of failure. RESULTS: Statistical analysis revealed no significant difference between wedge fixation and screw fixation (p = 0.16), or between individual groups (interference screw versus 11 mm versus 13 mm wedge fixation) (P = 0.35). CONCLUSIONS: Tibial tunnel fixation using an impacted wedge shaped bone block in anterior cruciate ligament reconstruction has comparable ultimate tensile strength to titanium interference screw fixation.

Assessment of radionuclide arthrography in the evaluation of loosening of knee prostheses.

BACKGROUND: Radionuclide arthrography (RNA) is an established technique in the evaluation of hip prostheses but there is scant literature on its role in knee prostheses and no data specifically related to unicompartmental knee prostheses. We reviewed our experience with radionuclide arthrography in total (TKRs) and unicompartmental (UKRs) knee arthroplasties. METHODS: A retrospective review of 66 consecutive RNA studies that either had direct surgical correlation or arthroscopic assessment in conjunction with at least 12 months of clinical and radiological follow-up. These formed the basis of our case note review. 26 studies had a confirmed diagnosis of prosthetic loosening. RESULTS: By using standardised criteria for diagnosis and an early and late imaging protocol at 30 min and 4 h, RNA had an overall sensitivity of 88% and a specificity of 88% for the diagnosis of prosthetic loosening. The individual sensitivities and specificities were 93% and 86% for TKRs and 82% and 92% for UKRs. The technique was unable to detect femoral component loosening unless a long femoral stem was present, although only 8% of episodes of prosthetic loosening did not involve the tibial component. CONCLUSION: Radionuclide arthrography should be considered as a useful diagnostic test for the evaluation of loosening of the tibial component of knee prostheses but requires early and late imaging and close attention to detail to achieve optimal results.

Single photon emission computed tomography in planning unicompartmental knee arthroplasty. A prospective study examining the association between scan findings and intraoperative assessment of osteoarthritis.

The aim of this study was to determine the relationship between preoperative single photon emission computed tomography (SPECT) scan findings and intraoperative assessments of knee osteoarthritis (OA) in patients undergoing tibiofemoral unicompartmental knee arthroplasty (UKA). Fifty knees in 46 patients undergoing UKA were investigated preoperatively with a SPECT scan to confirm unicompartmental disease. There were 38 men and 12 women in the cohort with an average age of 63 years (range 44-78). The SPECT scan uptake in each compartment of the knee was graded by a single radiologist and these findings were compared with intraoperative assessments of OA (size and grade of lesion), made by two experienced surgeons, blinded to the scan findings. Significant association was demonstrated between scan findings and OA in all compartments of the knee (p<0.05), and this was strongest in the medial compartment and weakest in the patellofemoral compartment and lateral tibial plateau. We conclude that SPECT scan is a useful imaging modality in the planning of medial tibiofemoral UKA to confirm unicompartmental disease. The lower degree of association between scan findings and OA encountered in the patellofemoral compartments and lateral tibial plateau indicates that greater vigilance should be exercised in the intraoperative assessment of these areas.

Intraoperative arthrometry in anterior cruciate ligament reconstruction.

Arthrometry has an established role in the measurement of knee laxity in anterior cruciate ligament injury and following reconstruction. The role of routine intraoperative arthrometry in anterior cruciate ligament reconstruction is poorly defined, and this study was designed to test the hypothesis that intraoperative arthrometry provides an objective method of documenting successful knee stabilisation following anterior cruciate ligament reconstruction. A consecutive cohort of 100 patients with unilateral isolated anterior cruciate ligament disruption were prospectively evaluated using a Rolimeter arthrometer. A maximal manual force method was utilised by a single examiner. This allowed for side-to-side comparisons with the uninjured contralateral knee. Analysis of tibial translation was recorded preoperatively with patients both awake and asleep, intraoperatively following anterior cruciate ligament reconstruction, and postoperatively at 2 weeks and 3 months. Statistical analysis was performed using Spearman's correlation coefficients. Intraoperative arthrometry of anterior cruciate ligament reconstructed knees revealed statistically significant correlation with measurements of uninjured knees (p < 0.0001). These findings were reproducible at 2 weeks (p < 0.0001) and at 3 months (p = 0.0002). Based on our findings, we conclude that intraoperative arthrometry can be simple and provide reproducible results. It is a useful method of immediately and objectively documenting successful anterior cruciate ligament reconstruction.

Cement retrieval in minimally invasive knee surgery: the 90 degrees ball probe.

Minimally invasive knee surgery has many potential advantages as well as disadvantages. One such disadvantage in both unicompartmental and total knee arthroplasty is the inability to visualize or retrieve extruded cement. We describe the use of a new instrument, a 90 degrees ball probe, which we have used in more than 300 minimally invasive unicompartmental knee arthroplasty cases. It provides a simple, consistent, and safe method of cement retrieval.

Haemoglobin levels following unicompartmental knee arthroplasty: influence of transfusion practice and surgical approach.

A retrospective review was undertaken of preoperative and day 3 postoperative haemoglobin (Hb) levels in all unicompartmental knee arthroplasty (UKA) procedures performed by a single surgeon. Sixty-six UKAs were performed using the same prosthesis through an open approach with patella eversion. This group was compared with 212 UKAs performed using a minimally invasive approach without patella eversion, with an implant and instrumentation specifically devised for this approach. Both groups were well matched for patient demographics, surgical and anaesthetic techniques, thromboprophylaxis, and postoperative regimes. All patients received transfusions with pre-donated blood, except the unilateral minimally invasive approach group. An analysis of covariance was undertaken to examine the influence of the surgical approach and whether surgery was unilateral or bilateral, taking into account preoperative Hb levels and units of blood transfused. The average fall in Hb following UKA, adjusted for other variables, was 2.73 g/dl with an open approach compared to 1.82 g/dl with a minimally invasive approach. This difference was significant (p=0.0044). The average postoperative Hb in the minimally invasive group was 12.05 g/dl (range, 8.8 to 15.8 g/dl). Patients undergoing unilateral minimally invasive UKA are unlikely to develop symptomatic anaemia and should not be required to predonate blood or undergo transfusion.

Unicompartmental knee arthroplasty: an intermediate report of survivorship after the introduction of a new system with analysis of failures.

We describe the outcome of a series of 66 consecutive porous coated low contact stress (LCS) unicompartmental knee arthroplasty (UKA) cases performed in 52 patients for osteoarthritis (OA) by a single surgeon. Both survival, using the endpoint of revision for any cause, and knee function, using the Oxford knee score (OKS) as a validated outcome measure, were established in a retrospective review. At an average postoperative follow-up period of 5.9 years (range 5.1-6.6), there were 8 knees in patients who had died and 58 knees in those who were still living. We established the status of all knees, and prosthesis survival at 5 years was 89.7% (95% confidence interval, 81.6% to 97.7%). Technical errors were responsible for four of six failures and included progression of lateral compartment OA due to overcorrection, a medial tibial stress fracture due to poor pin placement, and a case where cement was required and poor cementing technique lead to early tibial component loosening. In the remaining 52 knees, the average preoperative OKS had improved significantly (p<0.0001) from 37.0 (range, 17-49) to a postoperative score of 20.5 (range, 13-32). We conclude that the functional results following UKA compare favourably to total knee arthropasty (TKA); however, the survivorship of this series does not match that of published reports of TKA. The introduction of a new system of UKA includes the risk of early failures due to surgeon error, even when a surgeon is competent in UKA, warranting careful surveillance during this period.