Impaired bone fracture healing leading to delayed union or pseudarthrosis is a multi-factorial phenomenon and can exert a significant impact on a person’s personality (personal and professional productivity), lifestyle, and ability to function—all of which compromise patients’ health-related quality of life, thus necessitating more aggressive approach [16, 17]. A severely deformed arthritic knees will produce abnormal load on tibia [10]. This repetitive eccentric load/stress may lead to fatigue fracture of the proximal tibia [18]. The incidence is expected to increase in the coming years, with an ageing population resulting in a greater number of tibial stress fracture associated with KOA, especially in Indian context. Correction of deformity axis and fracture healing are the two key issues that need to be addressed. Management can be either conservative or surgical. Conservative treatment can lead to disuse muscle atrophy, joint stiffness, osteoporosis, malunion and it will not restore the mechanical axis [19, 20]. On other hand, surgical intervention aims to eliminate pain, correct the deformity axis, achieve fracture healing and improve function [10, 21,22,23]. Opinions varied in the literature concerning the optimal treatment for the tibial stress fracture associated with varus OA knee. Most authors address this challenging problem by using modular stem prosthesis, which addresses both the deformity and symptoms of OA but has problems with durability and causes complications related to knee arthroplasty with a long tibial stem. Fracture fixation with loose-fitting stem is likely to increase the incidence of delayed union, thereby increasing the chances of non-union. In our experience, supplementary fixation was not needed if a snugly-fitted stem was in place. Loose stem and wide canal diameter warrant additional plate fixation to provide rotational stability. In the present series, three patients in the study group and four patients in the control group required additional fixation with a plate to achieve rigid rotational stability.
In the present prospective study, we found that PFR could significantly improve the functional outcome of the affected knee joint and minimize the risk of pseudarthrosis or delayed fracture union. There are several factors that might contribute to our results. First, PFR technique was used during primary surgery so as to allow longitudinal pressure at the fracture site. Second, a snugly-fitted stem and/or compression plate at the fracture site could provide rotational stability, thereby reducing the shearing forces. Finally, more efficient decompression of medial compartment with no residual varus led to correction of biomechanical axis. (Fig. 7).
The current study showed that significant number of patients [16 (51.61%)] in the control group had delayed fracture healing when compared to the study group (p < .05). In our control group, an intact fibula appears to be an important risk factor for delayed union. We believe that, the fibula acts as an important lateral strut and may therefore prevent approximation of the fragments, and thereby delay healing. Irigoyen Dotti mentioned the diminished pressure between the fragments, the influence of the interosseus membrane, and the persistence of a non-fractured fibula or a fibula that healed within the usual time were factors that led to delayed fracture union [24]. Furthermore, a gap at the fracture site is a critical factor that prolongs the healing time [25]. Delayed healing of a tibial stress fracture in the presence of an intact fibula pointed to resection of the fibula before non-union is established. Sixteen percent of patients in the control group reported established pseudarthrosis and underwent internal fixation (plate osteosynthesis) along with bone grafting as a standard treatment (Fig. 6). In the present series, an altered strain (due to tibiofibular length discrepancy), decreased compression force on the stress fracture site, and inadequate decompression of medial compartment owing to intact fibula led to delayed union and non-union in control group while failure to correct extra-articular deformity (S-shaped tibia) led to delayed union in one in the study group.
Furthermore, the lack of adequate compression or collapse at the fracture site and stem extension failure to bypass the fracture adequately could be a major factor in fracture healing and construct strength (Fig. 6).
In the present study we found PFR could completely correct preoperative varus alignment in the cohort when compared with control group (p < .05). Most patients in the control group had persistent residual varus alignment. The most likely explanation for this finding is the intra-operative difficulty associated with obtaining neutral alignment owing to medial soft tissue contracture and increased tension [26]. Increased risk of revision was associated with malalignment, particularly in varus [27,28,29]. Genu varum can be corrected by combination of larger soft tissue release, pie crusting and more complex bone cuts [30,31,32,33,34,35,36]. Though clinical benefit has been shown, unfortunately, these techniques require specific psychomotor skills. Furthermore, all these procedures results in more bleeding, more instability, thus potentially increasing joint trauma.
The patients in the study group had significantly better range of motion than the control group at the last follow-up. This difference could be attributed to delay in rehabilitation or compromised rehabilitation in the control group. The delay in rehabilitation was due to inadequate pain relief owing to delayed union and repeated surgical intervention for established pseudarthrosis. During the course of study, authors noticed that post-surgical pain delayed early rehabilitation and thus negatively affected patients’ satisfaction rate and functional outcomes [37].
In the current study, we started to use PFR as an additional procedure to decompress the medial compartment more efficiently. It was noticed that, during the surgery, in the PFR group, it was easier for us to restore the mechanical axis than in the control group. PFR releases soft tissue tension. Currently, it is difficult to discern underlying mechanism for the efficacy of PFR but it probably works by rebalancing or redistributing the load on the lateral and medial tibia plateau post surgery or due to non-uniform settlement theory [38, 39].
Authors articulated that corrective osteotomy alone, in the cases of an arthritic knee with extra-articular deformities, can facilitate the correction of malalignment. At times, PFR also facilitates the correction of alignment due to an associated extra-articular deformity by releasing tension. When extra-articular deformity associated with proximal stress fracture exists, we usually combine corrective osteotomy with PFR to correct the adverse biomechanics both at the joint and at the fracture site. Only corrective osteotomy in these cases would lead to delayed union or non-union with persistence of residual varus alignment. In the present series, four patients in the study group were treated by corrective osteotomy besides PFR and six patients in the control group received tibial osteotomy for correction of the extra-articular deformity. Authors noticed that all these six cases in the control group showed features suggestive of delayed union and residual varus alignment. The intact fibula in these cases impeded the adequate collapse at the fracture site and correction of the alignment. Authors recommend corrective osteotomy plus PFR in the cases of an arthritic knee associated with stress fracture and extra-articular deformity.
During follow-up, all patients showed statistically significant improvement in their WOMAC total scores (p < 0.05). Mean VAS scores were significantly lower than the preoperative data. Treatment group showed significantly greater improvement than control group (p < 0.05). The answer probably lies in a combination of reasons: the control group had delayed fracture healing and non-union (16%) and persistent residual varus alignment.
Currently, we believe that due to the lack of biomechanical data, this supposition remains empirical. However, our findings suggest that the present technique addresses all concerned issues. Furthermore, authors believe that the present technique can be used as routine procedure for the correction of all varus deformities associated with stress fractures as it has the potential to correct significantly-deformed knee, improve the altered biomechanics and enhance the fracture healing without disturbing the soft tissues. This in turn could reduce the risk of delayed healing and/or ununited stress fractures, residual varus, and morbidity and thereby improve the functional outcome. In the cohort of the current study, no PFR-related complication was reported.
There were some limitations to the current study. First, we analyzed only varus knees. Therefore the findings of current study cannot be directly applied to valgus knees. Further studies should investigate its efficacy in the cases of valgus knee. Second, current study reported subjective outcome measures for patients with knee osteoarthritis and this may lead to biased evaluations. Further research using biomechanical data is warranted. Third, the small sample size in this research prevents the generalization of the finding and typically leads to Type-II errors. Despite these limitations, to the best of our knowledge, this is the first pilot report which critically analyzed the impact of proximal fibular resection on the severely varus-deformed arthritic knees associated with tibial stress fracture. These preliminary findings provide a rationale for future research using randomized controlled trials with larger sample sizes, and exploration into routine use of proximal fibular resection in patients with severely-deformed knee associated with stress fractures and its effect on biomechanical outcomes.