Comment on: Measurement of the knee joint line in Turkish population

To the Editor,

We read with interest the article entitled “Measurement of the knee joint line in Turkish population” by Gürbüz et al in Vol. 49, No. 1 (2015) of your journal.¹ We congratulate them for their inspiring work.

The authors measured the femoral width, the distance from the apex of the fibular head to joint line and the distance from the adductor tubercle to the joint line to determine the knee joint line level relative to these landmarks and the correlation of relative distance of joint line level to the femoral width. However, the study itself has some methodological drawbacks;

• A total of 117 knees were included in the study, but the number of patients was 108. That means nine patients were recorded twice with right and left knee measurements. This is not appropriate from the statistical point of view since joint line levels relative to specific landmarks for individuals are not expected to be different in each knee. Therefore, to our knowledge, all the studies in the literature cover only one leg for this type of morphometric studies; otherwise, bilateral measurements should be evaluated in separate groups.^{2 ; 3 ; 4  ;  5}
• To ensure images representative of normal anatomy, patients with preexisting radiologic evidence of arthritis in their knees should be excluded from the study.^{2 ; 3 ; 4  ;  5} However, the exclusion criteria of the authors did not cover knee osteoarthritis that definitely may alter joint level measurements due to erosions of the subchondral bone as seen in Fig. 1 in the original article (knee with Kellgren–Lawrence Grade 3 osteoarthritis and possible valgus deformity). In addition, the patella in the figure showing the knee joint should have been centered, since it is one of the criteria of the study.
• The results of the statistical analysis given in the article are very preliminary to understand the relationship between variables in details. For instance, just by reporting the R² value for linear regression analysis, we could estimate what percentage of the variability in the dependent variable (adductor tubercle joint line level-AJD) is explained by the independent variable (femoral width-FW).

In reply,

Thank you for your interest in our article. We included 117 knees of 108 patients in the study. The bilateral measurement percentage was 8%, though some studies include bilateral measurement of up to 25%.^{1 ; 2 ; 3  ;  4} The mean age of patients was 31.3 years (range: 16–82 years). Our study comprises a wide age range, but only 7 patients were over 60 years old. Similar studies have used an age group of up to 89 years old.^{4 ; 5  ;  6} We thank for your comment, because the patella must be centralized, but unfortunately that figure was overlooked. A statistician performed the statistical analysis, but the data may need to be evaluated by another statistician.

Dr. Murat Çakar

Address: Okmeydanı Eğitim ve Araştırma Hastanesi, Ortopedi ve Travmatoloji Kliniği, İstanbul, Turkey

Tel: +90 212 – 424 05 05

E-mail: drmuratcakar@gmail.com

References

1. 1 E. Havet, A. Gabrion, F. Leiber-Wackenheim, J. Vernois, B. Olory, P. Mertl; Radiological study of the knee joint line position measured from the fibular head and proximal tibial landmarks; Surg Radiol Anat, 29 (2007 Jun), pp. 285–289 Epub 2007 Apr 18
2. 2 H.E. Figgie 3rd, V.M. Goldberg, K.G. Heiple, H.S. Moller 3rd, N.H. Gordon; The influence of tibial-patellofemoral location on function of the knee in patients with the posterior stabilized condylar knee prosthesis; J Bone Joint Surg Am, 68 (7) (1986 Sep), pp. 1035–1040
3. 3 T.F. Wyss, A.J. Schuster, P. Münger, D. Pfluger, U. Wehrli; Does total knee joint replacement with the soft tissue balancing surgical technique maintain the natural joint line?; Arch Orthop Trauma Surg, 126 (7) (2006 Sep), pp. 480–486
4. 4 E. Vignon, M. Piperno, M.P. Le Graverand, et al.; Measurement of radiographic joint space width in the tibiofemoral compartment of the osteoarthritic knee: comparison of standing anteroposterior and Lyon schuss views; Arthritis Rheum, 48 (2) (2003 Feb), pp. 378–384
5. 5 K.A. Murshed, A.E. Ciçekcibaşi, A. Karabacakoğlu, M. Seker, T. Ziylan; Distal femur morphometry: a gender and bilateral comparative study using magnetic resonance imaging; Surg Radiol Anat, 27 (2) (2005 Apr), pp. 108–112
6. 6 J. Romero, B. Seifert, O. Reinhardt, et al.; A useful radiologic method for preoperative joint-line determination in revision total knee arthroplasty; Clin Orthop Relat Res, 468 (5) (2010 May), pp. 1279–1283

References

1. 1 H. Gürbüz, M. Çakar, M. Adaş, A.Ç. Tekin, M.K. Bayraktar, C.Z. Esenyel; Measurement of the knee joint line in Turkish population; Acta Orthop Traumatol Turc, 49 (2015), pp. 41–44 http://dx.doi.org/10.3944/AOTT.2015.14.0050 PMID: 25803252
2. 2 H.R. Gungor, N. Ok, K. Agladioglu, S. Akkaya, E. Kiter; Significance of asymmetrical posteromedial and posterolateral femoral condylar chamfer cuts in total knee arthroplasty; Knee Surg Sports Traumatol Arthrosc, 22 (2014), pp. 2989–2994
3. 3 J. Mountney, R. Karamfiles, W. Breidahl, M. Farrugia, J.M. Sikorski; The position of the joint line in relation to the trans-epicondylar axis of the knee: complementary radiologic and computer-based studies; J Arthroplasty, 22 (2007), pp. 1201–1207
4. 4 T.S. Rajagopal, D. Nathwani; Can interepicondylar distance predict joint line position in primary and revision knee arthroplasty?; Am J Orthop, 40 (2011), pp. 175–178
5. 5 E. Servien, D. Viskontas, B.M. Giuffrè, M.R. Coolican, D.A. Parker; Reliability of bony landmarks for restoration of the joint line in revision knee arthroplasty; Knee Surg Sports Traumatol Arthrosc, 16 (2008), pp. 263–269