Trevor J. Shelton

Do varus or valgus outliers have higher forces in the medial or lateral compartments than those which are in-range after a kinematically aligned total knee arthroplasty?: limb and joint line alignment after kinematically aligned total knee arthroplasty

Aims The aims of this study were to determine the proportion of patients with outlier varus or valgus alignment in kinematically aligned total knee arthroplasty (TKA), whether those with outlier varus or valgus alignment have higher forces in the medial or lateral compartments of the knee than those with in‐range alignment and whether measurements of the alignment of the limb, knee and components predict compartment forces. Patients and Methods The intra‐operative forces in the medial and lateral compartments were measured with an instrumented tibial insert in 67 patients who underwent a kinematically aligned TKA during passive movement. The mean of the forces at full extension, 45° and 90° of flexion determined the force in the medial and lateral compartments. Measurements of the alignment of the limb and the components included the hip‐knee‐ankle (HKA) angle, proximal medial tibial angle (PMTA), and distal lateral femoral angle (DLFA). Measurements of the alignment of the knee and the components included the tibiofemoral angle (TFA), tibial component angle (TCA) and femoral component angle (FCA). Alignment was measured on post‐operative, non‐weight‐bearing anteroposterior (AP) scanograms and categorised as varus or valgus outlier or in‐range in relation to mechanically aligned criteria. Results The proportion of patients with outlier varus or valgus alignment was 16%/24% for the HKA angle, 55%/0% for the PMTA, 0%/57% for the DLFA, 25%/12% for the TFA, 100%/0% for the TCA, and 0%/64% for the FCA. In general, the forces in the medial and lateral compartments of those with outlier alignment were not different from those with in‐range alignment except for the TFA, in which patients with outlier varus alignment had a mean paradoxical force which was 6 lb higher in the lateral compartment than those with in‐range alignment. None of the measurements of alignment of the limb, knee and components predicted the force in the medial or lateral compartment. Conclusion Although kinematically aligned TKA has a high proportion of varus or valgus outliers using mechanically aligned criteria, the intra‐operative forces in the medial and lateral compartments of patients with outlier alignment were comparable with those with in‐range alignment, with no evidence of overload of the medial or lateral compartment of the knee.

Heterotopic ossification around the knee after tibial nailing and ipsilateral antegrade and retrograde femoral nailing in the treatment of floating knee injuries

PurposeFloating knee injuries are relatively uncommon injuries. We report the prevalence, location, and severity of heterotopic ossification (HO) around the knee in patients treated with antegrade tibial intramedullary nailing and ipsilateral antegrade versus retrograde femoral intramedullary nailing as well as how the severity of HO around the knee affects knee range of motion (ROM).MethodsFrom 2004 to 2014, 26 floating knee injuries were included. Radiographs were reviewed to determine presence, location, and severity of HO. Post-operative knee ROM was determined.ResultsA significantly higher prevalence of HO around the knee was detected in the retrograde group (90%) compared to the antegrade group (43%) (pu2009=u20090.028). There was a trend for more HO into the patellar tendon occurring in 29% of patients in the antegrade group and 74% in the retrograde group (pu2009=u20090.069). The severity of HO was higher for the retrograde group 1.6u2009±u20091.0 compared to the antegrade group 0.4u2009±u20090.5 (pu2009=u20090.004). There was poor correlation between HO severity and knee ROM.ConclusionsTreatment of floating knee injuries with a retrograde femoral nail was demonstrated to result in a greater likelihood of developing HO and a greater severity of HO around the knee than if treated with an antegrade femoral nail. However, this increased severity of HO is unlikely to affect ROM.Level of evidence: III.

The Varus Knee

Osteoarthritis with a varus deformity is one of the most common deformities presenting for total knee arthroplasty. At the present time, there are various options for correcting a fixed varus deformity, but it is well accepted that accurate soft tissue balance with restoration of the mechanical alignment of the knee joint is critical to a successful outcome. Soft tissue release has evolved over the years, to more sequential and controlled releases of the medial supporting structures. Understanding the implications with soft tissue release is paramount to a successful total knee arthroplasty and restoration of accurate alignment.

CT-measurement predicts shortening of stable intertrochanteric hip fractures

PurposenIntertrochanteric (IT) hip fractures can be treated with sliding hip screws (SHS) or cephalomedullary nails (CMN) based on the stability of the fracture. This stability is affected by the initial impaction of the fracture which can be difficult to assess. The aim of this paper is to develop specific pre-operative computed tomography (CT) measurements of IT fractures which are predictive of post-operative shortening.nnnMethodsnA retrospective review was performed of 141 patients with AO/OTA 31A1 or 31A2 fracture patterns, who had pre-operative radiographs and CT scans, and who were treated with a SHS or a CMN. Pre-operative and post-operative imaging of IT fractures were analyzed for those fractures that shortened ≥15u202fmm post-fixation.nnnResultsn11 fractures shortened ≥15u202fmm with CMN being protective of shortening (6/36 SHS versus 5/105 CMN, pu202f=u202f0.0268). A novel measurement made on the pre-operative CT scan called the cortical thin point (CTP) detected differences between patients with <15u202fmm and ≥15u202fmm of post-operative shortening for the SHS group (pu202f=u202f0.0375). CTP was found to be a reliable predictor for post-operative shortening of ≥15u202fmm when a cutoff threshold of 9u202fmm was used in the SHS group (pu202f=u202f0.0161).nnnConclusionsnMeasuring the CTP is predictive of post-operative shortening after fixation of an IT fracture with a SHS. CMN fixation may be protective of shortening. Patients with a CTP of ≤9u202fmm are at risk for fracture site shortening of more than 15u202fmm when treated with a SHS.

Comparison of knee injury threshold during tibial compression based on limb orientation in mice

Our previous studies used tibial compression overload to induce anterior cruciate ligament (ACL) rupture in mice, while others have applied similar or greater compressive magnitudes without injury. The causes of these differences in injury threshold are not known. In this study, we compared knee injury thresholds using a prone configuration and a supine configuration that differed with respect to hip, knee, and ankle flexion, and utilized different fixtures to stabilize the knee. Right limbs of female and male C57BL/6 mice were loaded using the prone configuration, while left limbs were loaded using the supine configuration. Mice underwent progressive loading from 2 to 20u202fN, or cyclic loading at 9u202fN or 14u202fN (nu202f=u202f9-11/sex/loading method). Progressive loading with the prone configuration resulted in ACL rupture at an average of 10.2u202f±u202f0.9u202fN for females and 11.4u202f±u202f0.7u202fN for males. In contrast, progressive loading with the supine configuration resulted in ACL rupture in only 36% of female mice and 50% of male mice. Cyclic loading with the prone configuration resulted in ACL rupture after 15u202f±u202f8 cycles for females and 24u202f±u202f27 cycles for males at 9u202fN, and always during the first cycle for both sexes at 14u202fN. In contrast, cyclic loading with the supine configuration was able to complete 1,200 cycles at 9u202fN without injury for both sexes, and an average of 45u202f±u202f41 cycles for females and 49u202f±u202f25 cycles for males at 14u202fN before ACL rupture. These results show that tibial compression configurations can strongly affect knee injury thresholds during loading.

Mortality During Total Knee Periprosthetic Joint Infection

BACKGROUNDnPeriprosthetic joint infections (PJIs) are fraught with multiple complications including poor patient-reported outcomes, disability, reinfection, disarticulation, and even death. We sought to perform a systematic review asking the question: (1) What is the mortality rate of a PJI of the knee undergoing 2-stage revision for infection? (2) Has this rate improved over time? (3) How does this compare to a normal cohort of individuals?nnnMETHODSnWe performed a database search in MEDLINE/EMBASE, PubMed, and all relevant reference studies using the following keywords: periprosthetic joint infection, mortality rates, total knee arthroplasty, and outcomes after two stage revision. Two hundred forty-two relevant studies and citations were identified, and 14 studies were extracted and included in the review.nnnRESULTSnA total of 20,719 patients underwent 2-stage revision for total knee PJI. Average age was 66 years. Mean mortality percentage reported was 14.4% (1.7%-34.0%) with average follow-up 3.8 years (0.25-9 years). One-year mortality rate was 4.33% (3.14%-5.51%) after total knee PJI with an increase of 3.13% per year mortality thereafter (rxa0= 0.76 [0.49, 0.90], P < .001). Five-year mortality was 21.64%. When comparing the national age-adjusted mortality (Actuarial Life Table) and the reported 1-year mortality risk in this meta-analysis, the risk of death after total knee PJI is significantly increased, with an odds ratio of 3.05 (95% confidence interval, 2.69-3.44; P < .001).nnnCONCLUSIONnThe mortality rate after 2-stage total knee revision for infection is very high. When counseling a patient regarding complications of this disease, death should be discussed.

Implant Survival and Function Ten Years After Kinematically Aligned Total Knee Arthroplasty

BACKGROUNDnAlignment in the varus or valgus outlier range of the tibial component, knee, and limb might adversely affect the long-term results of kinematically aligned total knee arthroplasty (TKA) particularly when patients are selected without restricting the degree of preoperative varus-valgus and flexion deformity.nnnMETHODSnA retrospective review of all patients treated in 2007 with a primary TKA determined the 10-year implant survivorship, yearly revision rate, Oxford Knee Score, and WOMAC. All 222 knees (217 patients) were aligned kinematically using patient-specific instrumentation without restricting the degree of preoperative deformity and with the restoration of the native joint lines and limb alignment. Mechanical alignment criteria categorized the alignments of the tibial component, knee, and limb as in-range or in a varus or valgus outlier range.nnnRESULTSnThe implant survivorship (yearly revision rate) was 97.5% (0.3%) for revision for any reason and 98.4% (0.2%) for aseptic failure. The percentage postoperatively aligned in the varus outlier (valgus outlier) range was 78% (0%) for the angle between the tibial component and mechanical axis of the tibia, 31% (5%) for the tibiofemoral angle of the knee according to the criteria by Ritter etxa0al, and 7% (21%) for the hip-knee-ankle angle of the limb according to the criteria by Parratte etxa0al. Patients grouped in the varus outlier range, valgus outlier range, and in-range had similar implant survival and function scores. The 10-year Oxford Knee Score (48 best) and WOMAC (0 best) averaged 43 and 7 points, respectively.nnnCONCLUSIONnWith the limitation that a large case series unlikely represents the full range of preoperative deformities and native alignments, treatment of patients with kinematically aligned TKA with patient-specific instrumentation without restricting the preoperative deformity did not adversely affect the 10-year implant survival, yearly revision rate, and level of function.nnnLEVEL OF EVIDENCEnLevel III, therapeutic study.

Anterior centre-edge angle on sagittal CT: a comparison of normal hips to dysplastic hips

Purpose: The anterior centre-edge angle (ACEA) describes anterior acetabular coverage on false profile radiographs. Variability associated with pelvic tilt, radiographic projection, and identifying the true anterior edge, causes discrepancies in measuring an accurate ACEA. Computed tomography (CT) has the potential of improving the accuracy of ACEA. However, because the ACEA on sagittal CT has been shown to not be equivalent to ACEA on false profile radiographs, the normal range of ACEA on CT currently remains unknown and cannot reliably be used to determine over/under coverage. We therefore asked: what is the normal variation of ACEA corrected for pelvic tilt on sagittal CT and how does this compare to dysplastic hips? Material and Methods: A retrospective review was conducted on patients 10–35 who underwent CT for non-orthopedic related issues and patients with known hip dysplasia. The ACEA was measured on a sagittal slice corresponding to the centre of the femoral head on the axial slice and adjusted for pelvic tilt. A statistical comparison was then performed. Results: A total of 320 normal patients and 22 patients with hip dysplasia were reviewed. The mean ACEA for all ages was 50° ± 8°, (range: 23–81º), with a larger mean ACEA for males (51°) than females (49°). The ACEA mean for dysplastic hips was 30° ± 11° with a statistically significant difference in mean from the normal hip group (p < 0.0001). Conclusion: The ACEA can be reliably measured on sagittal CT and significantly differs from dysplastic hips. ACEA measurements above 66° or below 34° may represent anterior over and under coverage.

Self-Resolution of a Draining Sinus Tract in a Patient with Chronic Periprosthetic Hip Infection

We report a novel case of a patient who had a draining sinus soon after a total hip arthroplasty that spontaneously resolved. The patient voluntarily discontinued antibiotic suppressive therapy (AST) after 10 years of treatment and paradoxically experienced full resolution of signs of chronic prosthetic joint infection (PJI), including recovery of his left-sided draining sinus tract. Now 8 years after discontinuing AST, the patient has no pain, good function, and no major or minor criteria of joint infection according to the Musculoskeletal Infection Society (MSIS) workgroup. The authors have not identified literature describing a similar resolution of draining sinus tracts from around a prosthetic joint after discontinuing AST. Despite the resolution of this patients sinus tract, the authors do not advocate for discontinuing AST in patients with a draining sinus tract. However, in spite of the fact that the MSIS consensus statement suggests that a draining sinus is a sure sign of PJI and that the assumption is that the infection will not go away until explant, this case was different.