Tasman Medical Journal

ISSN:  2652-1881

Volume 2020 - Issue 2.

Modelling community spread of Covid-19 without complex mathematics

J. Alasdair Millar


Aim:  Current modelling of Coronavirus (Covid-19) spread relies on complex mathematical equations.  I wished to develop a simple spreadsheet model that will allow the public to understand the dynamics of Covid-19 infection without the need to comprehend the underlying equations.

Methods:  A simple spreadsheet model taking up 5 columns of cumulative calculations was developed for a population of 1 m.  Each row represented a 6-day cycle.  The known infection rate Ris applied to currently infectious persons but is adjusted downwards as the proportion of the population that remains susceptible declines.  Social restrictions designed to slow the spread of the virus were represented in reduced Rvalues.  Deaths were estimated at the reported global mortality rate.

Results:  In the baseline model without restrictions there was a delay of 55 days before the rate of increase increased rapidly in an exponential manner to a peak at 85 days and cessation of further infections after 100 days.  All but 21,000 (2.1%) became infected. There was a peak of 32,000 infections in any one 6-day cycle.  A substantial progressive reduction in peak infections were found as R was reduced, but the duration of period of infections increased.  At very low values of R the lengthening of the curves became substantial, indicating chronic low-level viral activity.

Conclusions:  The model successfully reproduced qualitatively the main results of sophisticated modeling.  It supported the notion that viral control can be achieved by taking early draconian measures to reduce the spread and prevent overwhelming pressure on the health system.  It also clarified that reducing the peak effect comes at a price of prolonging the epidemic, potentially producing a chronic steady state at low infection rates.

Tasman Medical Journal 2020; 2: 35-40.


Isolated meniscal repair is not inferior to meniscal repair combined with ACL reconstruction, and shows improved outcomes six-months after surgery

Navendu Goyal, Piers Yates, Christopher Jones, Jay Ebert and Peter D'Alessandro



Purpose: We measured short-term (6-months) clinical and functional outcomes and revision rates after arthroscopic meniscal repair with and without ACL reconstruction.

Materials and Methods: Forty-two patients who underwent meniscal repair over a 2-year period with a minimum 6-month follow up period were included.  Outcomes were measured by visual analogue pain score, KOOS, WOMAC and SANE scoring systems.

Results: Ten procedures were isolated repairs and 32 were in conjunction with ACL reconstruction.  All menisci were repaired using the All-Inside FAST-FIX 360 System (Smith and Nephew, UK).  Four patients required additional Inside-Out sutures, and 2 required Outside-In. A total of 4 Fast Fix 360 anchors and 1 Inside-Out Suture in 3 patients did not implant successfully and required intra-operative removal.  Pre-operative KOOS pain scores improved from a mean of 68.8±17.1 (SD) to 82.7±12.8 at the 6-month evaluation (p<0.001).  Corresponding KOOS symptom score also improved significantly from 62.6±17.9 to 77.8±14.3 (p<0.001), as did mean preoperative KOOS ADL from 73.6±19.6 to 89.5±13.3 (p<0.001).  Sports and recreation function increased from 32.1 to 59.5 at 6 months post operatively (p<0.001), and knee-related quality of life improved from 31.4±17.0 to 55.0±18.4 (p<0.001).  WOMAC and SANE scores showed corresponding improvements.  There was no significant difference in the outcome scores of patients with or without ACL reconstruction. Two patients required revision surgery due to further tears.

Conclusions:Meniscal repair is an effective procedure leading to excellent patient reported outcome measures with low rates of revision, even in isolated procedures without ACL Reconstruction. The FAST-FIX 360 system was found to be a reliable system for all-inside meniscal repair.